From: TSS()Subject:
Sheep can pass BSE to their lambsDate: September 2, 2005 at 7:56 pm PST

Sheep can pass BSE to their lambs16:34 17 August 2005 NewScientist.com news service Debora MacKenzie

BSE has been shown to spread naturally between sheep for the first time. It passed from mother to lamb, before or during birth, in an experimentally infected flock. But if the study shows the infection spreads more generally within the flock, that means BSE could still be lurking in Europe’s sheep, possibly posing a greater health risk to people than that from “mad” cows.

Scientists found in 1996 that sheep develop a disease similar to BSE if they eat infected cattle tissue. But feeding cattle remains to sheep was banned in Britain in 1988, and in the EU in 1994. All the sheep infected before then should be gone by now.

So there should be no more BSE sheep – unless they can transmit BSE to each other. Cattle cannot do this, but sheep transmit a related disease called scrapie between themselves, apparently when they eat placentas and other birthing remains in the field. If BSE also spreads “horizontally” in this way – between other members of the flock – it might have kept spreading in sheep even after the feed ban.

And because the symptoms of BSE in sheep resemble scrapie, “mad” sheep might not have been noticed. Nearly 2700 sheep with apparent scrapie have now been tested for BSE in the UK. None so far had clear BSE, though two are being tested further. BSE-infected goats, which are biologically similar to sheep, were found in France and possibly the UK in 2005.

BSE-infected sheep are potentially more dangerous to human consumers than BSE-infected cows, as they carry the infection in more of the tissues people eat.

Mother to lambSue Bellworthy and colleagues at the UK’s Veterinary Laboratories Agency (VLA) report that two ewes experimentally infected with BSE in a flock in Warwickshire in 2000 gave birth to lambs in 2003 that died of BSE this year. This is the first confirmation of “vertical” transmission of BSE from mother to offspring. It has been suspected but never proved in cattle.

In sheep, given how scrapie spreads, “this was expected,” Danny Matthews, a BSE expert at the VLA, told New Scientist. “But vertical transmission alone would not be enough to keep BSE going in the sheep population after the feed ban.” Transmission would be limited to one family line, which would die out as animals die of BSE or are eaten.

The experimental herd is now being watched to see if adults can transmit BSE horizontally to other ewe’s lambs now being born and raised within the flock. So far none has, and no uninfected adult sheep have caught the disease from experimentally infected sheep. But it’s still “too early to say”, cautions Matthews.

Journal reference: Veterinary Record (Aug 13, p 206)

BSE and vCJD - Learn more in our comprehensive special report.

http://www.newscientist.com/channel/health/bse/dn7861

British goat may have harboured BSE18:34 08 February 2005 NewScientist.com news service Debora MacKenzie

A British goat which died in 1990 may have had BSE, UK government officials revealed on Tuesday. The discovery means the infection may have circulated in goats in the past, and may even be circulating at low levels today.This follows the recent disclosure of the first natural case of BSE to be found in a goat - a French animal that died in 2002. New Scientist has learned that the British goat was discovered as a result of the French case, as UK government scientists prepared for the increased testing of goats after the discovery.

It has long been assumed that sheep and goats may have been exposed to BSE in feed made from infected cattle. But unlike cattle, both creatures can transmit such infections between individuals, which might have kept the disease circulating after infected feed was banned.

BSE in sheep and goats would also be hard to spot, as both can naturally develop a similar disease called scrapie which has the same symptoms, although it is not thought to pose a risk to human consumers. And, unlike cattle, sheep experimentally infected with BSE carry the infectious prion in muscle meat, so the infection in sheep and goats could pose more of a risk to consumers.

For these reasons European Union countries have been testing sheep and goats for BSE since 2002. These tests discovered the infected French goat.

Telling the difference"We were involved in helping evaluate the French data in December," says Danny Matthews of the UK's Veterinary Laboratories Agency, the EU reference lab for BSE. It was clear that the EU would probably ask for increased testing in goats as a result, he says.

In fact, from February, 80% of healthy slaughtered goats over the age of 18 months, plus "high risk" goats such as those found dead or unable to stand, should be tested, officials have just agreed. Three different test methods - called western blot, ELISA and immunohistochemistry (IHC) - will be used to distinguish scrapie from BSE.

"We haven't had to test many goats in the UK," says Matthews. "We thought we should test our current IHC on goat brain to make sure it distinguishes BSE." Besides goats and sheep experimentally infected with scrapie or BSE, they tested two brain samples at random from within a selection of goats thought to have died of scrapie.

One of them gave an IHC result that looked like BSE. "We can't do the other two tests as we processed all the tissue we had from that animal for IHC," says Matthews. But the team will nevertheless attempt to extract enough tissue from the IHC test material to do the definitive BSE test. This involves injecting tissue into mouse brain to see if BSE develops. But that will not yield results for two years.

"What is important now is not what happened back in 1990, but whether the infection is still circulating in goats," notes Matthews.

http://www.newscientist.com/channel/health/dn6987

Like lambs to the slaughter

* 31 March 2001* Debora MacKenzie* Magazine issue 2284

Suspect symptoms

What if you can catch old-fashioned CJD by eating meat from a sheep infected with scrapie?

Exclusive from New Scientist magazine

Four years ago, Terry Singeltary watched his mother die horribly from a degenerative brain disease. Doctors told him it was Alzheimer's, but Singeltary was suspicious. The diagnosis didn't fit her violent symptoms, and he demanded an autopsy. It showed she had died of sporadic Creutzfeldt-Jakob disease.

Photo: Murdo McLeod

Most doctors believe that sCJD is caused by a prion protein deforming by chance into a killer. But Singeltary thinks otherwise.

He is one of a number of campaigners who say that some sCJD, like the variant CJD related to BSE, is caused by eating meat from infected animals. Their suspicions have focused on sheep carrying scrapie, a BSE-like disease that is widespread in flocks across Europe and North America.

Now scientists in France have stumbled across new evidence that adds weight to the campaigners' fears. To their complete surprise, the researchers found that one strain of scrapie causes the same brain damage in mice as sCJD.

"This means we cannot rule out that at least some sCJD may be caused by some strains of scrapie," says team member Jean-Philippe Deslys of the French Atomic Energy Commission's medical research laboratory in Fontenay-aux-Roses, south-west of Paris.

Hans Kretschmar of the University of Göttingen, who coordinates CJD surveillance in Germany, is so concerned by the findings that he now wants to trawl back through past sCJD cases to see if any might have been caused by eating infected mutton or lamb.

Brain damage

Scrapie has been around for centuries and until now there has been no evidence that it poses a risk to human health. But if the French finding means that scrapie can cause sCJD in people, countries around the world may have overlooked a CJD crisis to rival that caused by BSE.

Deslys and colleagues were originally studying vCJD, not sCJD. They injected the brains of macaque monkeys with brain from BSE cattle, and from French and British vCJD patients. The brain damage and clinical symptoms in the monkeys were the same for all three. Mice injected with the original sets of brain tissue or with infected monkey brain also developed the same symptoms.

As a control experiment, the team also injected mice with brain tissue from people and animals with other prion diseases: a French case of sCJD; a French patient who caught sCJD from human-derived growth hormone; sheep with a French strain of scrapie; and mice carrying a prion derived from an American scrapie strain.

As expected, they all affected the brain in a different way from BSE and vCJD. But while the American strain of scrapie caused different damage from sCJD, the French strain produced exactly the same pathology.

Multiple strains

"The main evidence that scrapie does not affect humans has been epidemiology," says Moira Bruce of the neuropathogenesis unit of the Institute for Animal Health in Edinburgh, who was a member of the same team as Deslys.

"You see about the same incidence of the disease everywhere, whether or not there are many sheep, and in countries such as New Zealand with no scrapie," she says. In the only previous comparisons of sCJD and scrapie in mice, Bruce found they were dissimilar.

But there are more than 20 strains of scrapie, and six of sCJD. "You would not necessarily see a relationship between the two with epidemiology if only some strains affect only some people," says Deslys. Bruce is cautious about the mouse results, but agrees they require further investigation. Other trials of scrapie and sCJD in mice, she says, are in progress.

Deformed proteins

People can have three different genetic variations of the human prion protein, and each type of protein can fold up two different ways. Kretschmar has found that these six combinations correspond to six clinical types of sCJD: each type of normal prion produces a particular pathology when it spontaneously deforms to produce sCJD.

But if these proteins deform because of infection with a disease-causing prion, the relationship between pathology and prion type should be different, as it is in vCJD. "If we look at brain samples from sporadic CJD cases and find some that do not fit the pattern," says Kretschmar, "that could mean they were caused by infection."

There are 250 deaths per year from sCJD in the US, and a similar incidence elsewhere. Singeltary and other US activists think that some of these people died after eating contaminated meat or "nutritional" pills containing dried animal brain.

Governments will have a hard time facing activists like Singeltary if it turns out that some sCJD isn't as spontaneous as doctors have insisted.

Deslys's work on macaques also provides further proof that the human disease vCJD is caused by BSE. And the experiments showed that vCJD is much more virulent to primates than BSE, even when injected into the bloodstream rather than the brain. This, says Deslys, means that there is an even bigger risk than we thought that vCJD can be passed from one patient to another through contaminated blood transfusions and surgical instruments.

More at: Proceedings of the National Academy of Sciences (vol 98, p 4142)http://www.pnas.org/cgi/content/full/041490898v1

Correspondence about this story should be directed to letters@newscientist.com

Scrapie is a natural disease of sheep and goats. It is a slow and inexorably progressive degenerative disorder of the nervous system and it ia fatal. It is enzootic in the United Kingdom but not in all countries.

The field problem has been reviewed by a MAFF working group (ARC 35/77). It is difficult to assess the incidence in Britain for a variety of reasons but the disease causes serious financial loss; it is estimated that it cost Swaledale breeders alone $l.7 M during the five years 1971-1975. A further inestimable loss arises from the closure of certain export markets, in particular those of the United States, to British sheep.

It is clear that scrapie in sheep is important commercially and for that reason alone effective measures to control it should be devised as quickly as possible.

Recently the question has again been brought up as to whether scrapie is transmissible to man. This has followed reports that the disease has been transmitted to primates. One particularly lurid speculation (Gajdusek 1977) conjectures that the agents of scrapie, kuru, Creutzfeldt-Jakob disease and transmissible encephalopathy of mink are varieties of a single "virus". The U.S. Department of Agriculture concluded that it could "no longer justify or permit scrapie-blood line and scrapie-exposed sheep and goats to be processed for human or animal food at slaughter or rendering plants" (ARC 84/77)" The problem is emphasised by the finding that some strains of scrapie produce lesions identical to the once which characterise the human dementias"

Whether true or not. the hypothesis that these agents might be transmissible to man raises two considerations. First, the safety of laboratory personnel requires prompt attention. Second, action such as the "scorched meat" policy of USDA makes the solution of the acrapie problem urgent if the sheep industry is not to suffer grievously.

Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of sheep and goats were transmitted to squirrel monkeys (Saimiri sciureus) that were exposed to the infectious agents only by their nonforced consumption of known infectious tissues. The asymptomatic incubation period in the one monkey exposed to the virus of kuru was 36 months; that in the two monkeys exposed to the virus of Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and that in the two monkeys exposed to the virus of scrapie was 25 and 32 months, respectively. Careful physical examination of the buccal cavities of all of the monkeys failed to reveal signs or oral lesions. One additional monkey similarly exposed to kuru has remained asymptomatic during the 39 months that it has been under observation.

Dormont*, and Jean-Philippe Deslys* et al, that The agent responsiblefor French iatrogenic growth hormone-linked CJD taken as a control isvery different from vCJD but is similar to that found in one case ofsporadic CJD and one sheep scrapie isolate;